Vibrational therapy device used for resynchronization pacing in a treatment for heart failure

ABSTRACT

Systems for pacing the heart include a vibrational transducer which directs energy at the heart, usually at at least a ventricle, to pace the heart and to promote synchronized contraction of the ventricles. Optionally, additional vibrational and/or electrical stimulation may be provided. The vibrational transducers are usually implantable at a location proximate the heart.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 10/869,705 (Attorney Docket No. 021834-000620US), filed Jun. 15,2004, which claimed priority from U.S. Patent Application Ser. No.60/518,138 (Attorney Docket No. 021834-000600US), filed Nov. 6, 2003;and U.S. Patent Application Ser. No. 60/528,940 (Attorney Docket No.021834-000610US), filed Dec. 10, 2003, the full disclosures of which areincorporated herein by reference.

The disclosure of the present application is also related to thefollowing applications being filed on the same day as the presentapplication: U.S. patent application Ser. No. 10/869,776 (AttorneyDocket No. 021834-000130US); filed Jun. 15, 2004 (now U.S. Pat. No.7,006,864); U.S. patent application Ser. No. 10/869,242 (Attorney DocketNo. 021834-000210US), filed Jun. 15, 2004; and U.S. patent applicationSer. No. 10/869,631 (Attorney Docket No. 021834-000310US), filed Jun.15, 2004, the full disclosures of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The systems and methods of this invention relate to pacing treatment ofthe heart comprising applying vibrational energy.

Heart Failure (HF) currently affects over 5 million patients in theUnited States alone. This population has been steadily increasing due tooverall demographic aging and, in particular, the effects of newlife-prolonging treatments to patients with chronic cardiac conditions.HF is defined by ACC/AHA Task force as a complex clinical syndrome thatimpairs the ability of the ventricle to fill with or eject blood. Newmedications developed to treat HF have been generally ineffective, anddevice-based solutions appear to present a significant opportunity forafflicted patients.

HF generally results from one or more underlying factors includinghypertension, diabetes, valvular disease, cardiomyopathy, coronaryartery disease, or structural changes to the heart muscle. HF ischaracterized by reduced ventricular wall motion in systole and/ordiastole, and low ejection fraction. As the heart becomes less able topump sufficient volume to the system, patients develop symptoms of fluidretention, shortness of breath, and fatigue.

Approximately one third of patients with HF have poor timing ofcontraction between the right and the left ventricle and within the leftventricle, called interventricular and intraventricular dyssynchrony,respectively. This is sometimes also manifest by a wider than normal QRSinterval on a surface electrocardiogram (ECG) taken of a HF patient. Thewider than normal QRS interval is called conduction delay because thereis a prolonged time interval for the normal electrical impulse to travel(“conduct”) to all parts of both ventricles. This is also sometimesmanifest by conduction delay between the atria and ventricles (A-Vdelay). Ventricular dyssynchrony and conduction delays can contribute toweak left ventricular function by causing delayed and/or abnormal leftventricular contraction. There may be inadequate filling and emptying ofthe left ventricle, as well as backflow of blood into the left atrium,resulting in decreased cardiac output and increased symptoms for thepatient. This dysfunction causes increased mortality and morbidity amongpatients with HF.

Cardiac resynchronization therapy is the use of pacing to coordinate thecontraction of the ventricles in order to reduce heart failure andimprove prognosis in HF patients. Recently, devices that pace bothventricles, referred to as bi-ventricular pacing, have been adopted toprovide cardiac resynchronization therapy. A bi-ventricular pacingsystem utilizes conventional dual chamber, right atrium and rightventricle, pacing technology but adds a third lead, usually in acoronary vein, to sense and pace the epicardial surface of the leftventricle. The pacing device can then, at an appropriate time intervalafter right atrial activity, synchronize contraction of both right andleft ventricles either simultaneously or at coordinated time intervals.The synchronous contraction of the ventricles facilitates more adequatefilling of the left ventricle and less backflow (mitral valveregurgitation to the left atrium), resulting in more oxygenated bloodbeing pumped to the body. Alternatively, it has been shown that pacingonly the left ventricle at a location near the apex is associated withimprovement in left ventricular function. However, this location is notaccessible from the coronary veins in current pacing systems.

Clinical studies have shown a sustained improvement of symptoms andexercise tolerance in patients using bi-ventricular pacing devices toimprove left ventricular function. Cardiac resynchronization therapy hasalso been incorporated into implantable cardioverter defibrillator (ICD)devices, allowing for the simultaneous treatment of heart failure andthe prevention of sudden cardiac death caused by life-threateningventricular arrhythmias in HF patients.

Pacemaker leads are typically placed through the skin into a subclavianvein to access the venous side of the cardiovascular system. Inbi-ventricular pacing systems, one lead is placed in contact with theright ventricular wall and one lead is placed in contact with the rightatrial wall. To access the left ventricle, the third lead is passed intothe right atrium, into the orifice of the coronary sinus, and thenmaneuvered through the coronary veins to a position on the epicardialaspect of the lateral wall of the left ventricle. Some work has beendone exploring minimally invasive methods of alternatively placing thelead/electrode directly on the epicardium of the left ventricle.

Placement of the third lead to contact the left ventricle has been asignificant problem for application of this therapy. The coronary sinusis a complicated venous pathway with multiple branches which bend andnarrow with considerable variation as they extend distally onto theepicardium of the left ventricle. Placement of this lead requiressignificant skill on the part of the physician. In order to provideadequate steerability and pushability, the design of the leftventricular lead or a lead introduction system/device is much morecomplicated than for regular pacing leads. Often the left ventricularlead positioning/placement can take over an hour to perform exposing thepatient to increased fluoroscopy radiation and increased procedurerisks. Furthermore, in some patients (7.5% in the MIRACLE study), anacceptable lead placement is not possible due to anatomic constraints orundesirable phrenic nerve pacing. Additionally, lead dislodgement andloss of pacing capture have been a common complication in the use ofthese coronary sinus leads (e.g., 10-20% complication rates have beenreported within the first 6 months of device placement).

It would be beneficial to eliminate the third pacing lead and yetprovide resynchronization within the left ventricle and/or between theleft and right ventricles. Moreover, it would be beneficial to providemore physiological pacing of the right ventricle. In normal physiology,the right ventricle is first stimulated in the upper septal area, andthen the impulse travels down specially conducting pathways to the rightventricular apex. However, pacing from the right ventricle is virtuallyalways accomplished from a lead tip located in the right ventricularapex, such that the conduction pathway is abnormal and slow. Clinicaltrials have recently shown that in patients with and without A-V block,pacing from the right ventricular apex can result in increased totalmortality and re-hospitalization for heart failure compared to non-pacedpatients. The possible adverse effects of pacing the right ventricularapex in patients without bi-ventricular pacemakers is unknown, but asource of growing concern.

2. Description of the Background Art

This application has disclosure related to prior commonly assignedprovisional applications 60/479,347 (Attorney Docket No.21834-000100US), filed on Jun. 17, 2003; 60/496,184 (Attorney Docket No.21834-000110US), filed on Aug. 18, 2003; 60/496,179 (Attorney Docket No.21834-000200US), filed on Aug. 18, 2003; and 60/507,719 (Attorney DocketNo. 21834-000300US), filed on Sep. 30, 2003. The full disclosures ofeach of these prior filings are incorporated herein by reference.

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BRIEF SUMMARY OF THE INVENTION

For this invention, the use of a device to effect left ventricularpacing and/or to synchronize left ventricular pacing with rightventricular activation provides an improved method of treating patientswith heart failure or possibly of preventing heart failure. Theimprovement uses vibrational energy to effect left ventricular pacing tothe left ventricle without the use of an implanted intracardiac orepicardial lead in contact with the left ventricle. Optionally, a systemand method of the present invention may rely on delivery of thevibrational energy from an external source to provide temporary leftventricular pacing treatment for heart failure. The system described isa fully implanted subcutaneous device that provides ultrasound energy atfrequencies, amplitudes, and treatment durations that stimulate cardiactissue without the use of leads contacting left ventricular tissue.

A treatment regime for providing synchronized beating of the left andright ventricle is accomplished in part by applying a vibrational energywave. The vibrational wave stimulates the heart. Once stimulated, a QRScomplex can be seen on an electrocardiogram and contraction of the heartchamber(s) is initiated. In this invention, the wave will either a)simultaneously stimulate both ventricles to contract, b) stimulate theventricles in a preferred, more physiologic, conduction pattern, or c)be delivered in coordination with an electrical pacing and sensing lead,such that one ventricle is electrically paced and the vibrational wavestimulates the other ventricle. Vibrational energy offers the potentialbenefit of being able to stimulate without tissue contact, and,therefore, is not limited to the right ventricular apex as a pacing sitenor does it require direct placement and contact of a lead in or on theleft ventricle.

The vibrational wave can be applied to stimulate each heart beat withultrasound as a single burst or as multiple bursts with appropriateselection of the following parameters: Parameter Value Range Ultrasoundfrequency 20 KHz-5 MHz Burst Length (#cycles) 3-250 Pace Pulse Duration0.12 μS-13 mS Duty Cycle 0.1-100% Intensity >0.2 W/cm²

The device would contain one or more ultrasound transducers ofappropriate size and aperture to stimulate heart tissue within theultrasound beam. The transducer portion of the device would be implantedsubcutaneously in the anterior chest surface of the body in such fashionas to target the desired heart tissue within the beam profile of thetransducer. The beam profile would need only target a sufficient volumeof tissue to generate a vibrationally-induced paced beat. If the tissuevolume required for stimulation is small, a narrow beam could used.However, a wide beam could also be used and could successfully stimulatemultiple chambers simultaneously. Furthermore, multiple beams could beutilized to stimulate multiple sites within the heart, eithersimultaneously or sequentially per a programmable delay function.

In a combined electrical pacing and vibrational pacing device, thesynchronization of the delivery could be accomplished either within asingle enclosure or in two separate enclosures. Separate enclosureswould require communication between the devices to synchronize the beatsor detection of an electrically-paced beat by one device and animmediate vibrationally-paced beat response by the other device, orvice-versa.

As in all pacemaker devices, which include a variety of pacingmodalities, the delivery of the vibrational pacing energy could betriggered based on sensed or programmed heart rates or inhibited bysensed cardiac events in the atrium or ventricle. When used forbi-ventricular pacing, with vibrational pacing of the left ventricle incombination with electrical pacing of the right ventricle, thevibrational energy would be triggered to be synchronous, i.e.simultaneous or at a programmable delay, from the right ventricleelectrically-paced beat. Fundamentally, if a right ventricular beat istriggered or sensed by the vibrational device, then vibrational energyis delivered to the left ventricle to synchronize the chambers.

In the simplest form, the device would contain a vibrational energydelivery mechanism to stimulate the left ventricle. It would provide afixed programmable heart rate that stimulates a paced beat of the leftventricle via vibrational energy. The paced beat would then normallyconduct to the right ventricle. This would be analogous to a ventricularpacing and sensing (with inhibition) referred to as a VVI pacingmodality. An enhanced pacing modality referred to as VVI/T also includesprogrammability to trigger a paced beat in response to a sensed beat.

In a more complex form, the device would contain multiple vibrationalenergy mechanisms to stimulate the heart tissue at multiple points,e.g., at multiple locations within the left ventricle, and/or withinboth the left and right ventricles. Stimulation could occur eithersimultaneously, or sequentially per a programmable function.

In the most complex form, the device would contain a vibrational energydelivery mechanism for left ventricular stimulation and also containelectrical capabilities for pacing and sensing of both right atrial andright ventricular chambers with programmable capabilities for allcombinations of pacing modalities (e.g. DDDR+, Dual chamber pacing, Dualchamber sensing, Dual chamber triggered and inhibited modes with Rateresponsive sensors and mode adaptation). Optionally, the device wouldcontain the capability for high energy delivery used for cardioversionand defibrillation, using either electrical energy or vibrationalenergy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate two embodiments with one or more right-sidedtransvenous leads; a left-sided transducer over or between the ribs witha left-sided canister implant (FIG. 1A), and a medial transducerplacement over the sternum with a right-sided canister implant (FIG.1B).

FIG. 2A and 2B illustrate an alternative embodiment without leads and acanister housing the ultrasound transducer implanted in the leftprecordial subcutaneous space.

FIGS. 3A and 3B illustrate an alternative embodiment with one or moresubcutaneous leads attached to a canister implanted in the leftprecordial subcutaneous space.

FIG. 4 illustrates an alternative embodiment with two right-sidedtransvenous leads, a ventricular lead incorporating a transducer withinthe lead body and an atrial lead, and a canister in the rightsubcutaneous space.

FIG. 5 illustrates a lead design incorporating an electrode pair at thedistal end for pacing and sensing, and one or more transducers withinthe body of the lead.

FIG. 6 is a block diagram showing an embodiment of the control circuitryimplementation of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In one exemplary embodiment, all the device sensing, logic and energysource components are housed within a single canister 10 implantedbeneath skin and adipose tissue in the left (FIG. 1A) or right (FIG. 1B)subclavian region of the chest wall. In this embodiment, electricalleads 12 containing electrodes are passed transvenously through thesuperior vena cava into the right atrium and/or right ventricle. Anultrasound transducer 14 is separately connected to the canister by acable 16. The transducer is encased in an appropriate housing and issubcutaneously implanted over the ribs, over the sternum, or between theribs in order to target the preferred region of the left or rightventricle within the ultrasound beam profile. The connecting cable 16 istunneled subcutaneously to the canister and connected.

Alternatively, two canisters may be implanted subcutaneously beneathskin and adipose tissue (not shown). The first canister houses thedevice sensing, logic and energy source components required for theelectrical pacemaker/cardioverter/defibrillator and may be implanted onthe left or right subclavian regions. The second canister is located inthe left anterior chest region over the ribs or between the ribs or itis located over the sternum. The second canister houses the transducer,device sensing, logic, and energy source for pacing using vibrationalenergy. A connecting cable is tunneled subcutaneously between the twocanisters.

In another embodiment, (FIGS. 2A and 2B), the device 20 is a singlecanister with no transvenous leads. As previously disclosed the devicecan be subcutaneously implanted in the left anterior chest region orover the sternum with the ultrasound beam(s) directed to theventricle(s) from a transducer within the canister. This represents aprogrammable rate VVI/T device that paces only the left ventricle orsimultaneously or sequentially paces the left and right ventricles usingvibrational energy. An electrocardiogram sensing circuit wouldpreferably be provided in this embodiment with electrodes on the surfaceof the canister, and would provide either an inhibited pacing operationwith a detected ventricular beat or a synchronized pacing operation witha detected ventricular beat.

In another embodiment, (FIGS. 3A and 3B), the device 22 is a singlecanister housing the sensing, logic, and energy source components forpacing using vibrational energy. One or more subcutaneous leads 24 and26 containing one or more vibrational energy elements arranged linearlyor in another pattern are connected to device 22. Electrodes for sensingof the electrocardiogram (sensors) are provided on either or both leads24 and 26 or the surface of the canister. This represents an alternativeprogrammable rate VVI/T device that paces either the left ventricle orsimultaneously or sequentially paces the left and right ventricles usingvibrational energy.

In another embodiment (FIG. 4), the device 30 is a single canister withtransvenous lead 32 containing capability for electrical sensing andpacing and transvenous lead 34 containing capability for electricalsensing and pacing and vibrational pacing. The single canister 30 wouldbe implanted beneath skin and adipose tissue in the left or rightsubclavian region. In this embodiment, the right ventricular lead 34(FIG. 5) containing both electrical and vibrational energy components,and a right atrial lead 32 containing electrical energy components areutilized. The leads are passed transvenously through the superior venacava into the right ventricle and the right atrium. In this embodimenttransducer(s) 36 would be contained within the body of the rightventricular lead. The transducer(s) 36 would deliver vibrational energyto pace one or both ventricles. The electrical component of the rightventricular lead would primarily be used for sensing, but couldoptionally be used for electrical pacing. The right atrial lead would beused for both sensing and pacing.

Another embodiment would be similar to FIG. 4, except that both theright atrial lead 32 and right ventricular lead 34 would contain bothelectrical 37 and 38 and vibrational 36 energy components as shown inFIG. 5. In this embodiment, the right atrial lead would function in amanner similar to the right ventricular lead, to accomplish pacing andsensing of the right and left atria.

Alternatively, the right atrial lead 32 would not be present, and theright ventricular lead would be as shown in FIG. 5 with an addedelectrical sensing electrode (not shown) located on a proximal portionof the lead such that the electrode would be positioned within the rightatrium.

Alternatively, the right atrial lead would not be present, and the rightventricular lead would be as shown in FIG. 5 with an added electricalsensing electrode (not shown) and with an added vibrational energytransducer (not shown) located on a proximal portion of the lead suchthat the components would be positioned within the right atrium. In thisembodiment a single lead could provide pacing and sensing of the rightand left atria and separately pacing and sensing of the right and leftventricles.

FIG. 6 provides a block diagram of circuitry for implementing the mostcomplex version of the device including dual chamber sensing, dualchamber electrical pacing, electrical cardioversion and defibrillation,and vibrational energy pacing. Alternatively, the cardioversion anddefibrillation may be provided by vibrational energy.

The device designs and implementations referred to thus far aregenerally useful for the treatment of patients with heart failure. Thetreatment of heart failure, however, may be accomplished with systemswhich may be somewhat simpler that those described above to promotetemporary synchronized contraction of the ventricles. In particular, thevibrational transducers may be adapted for manual control by either thepatient or by a doctor or other medial personnel. Most simply, thevibrational transducer may be incorporated into external units capableof being applied to the anterior chest (not shown). Usually, the patientwill be reclining on the table or bed, the vibrational transducer,attached by a cable to an external generator, is applied over thepatient's chest, preferably using a gel layer to enhance contact.Usually, the transducer will be placed generally over the ventricularregion of the heart and the transducer may be configured to directenergy over specific ventricular regions.

Systems embodied for external use have sensor circuitry, controlcircuitry, power supply, and burst generation incorporated into thegenerator (not shown). The ECG sensors may be incorporated into thetransducer housing or optionally standard transcutaneous electrodes maybe connected to the body and to the generator via cables. Alternatively,the generator may accept ECG signals directly from an externalelectrocardiogram system. Intrinsic heart signals detected from ECGsensors are analyzed by control circuitry and are used to control pacingusing the vibrational energy as discussed above for implantable systems.

1. A method for pacing the heart, the method comprising directingvibrational pacing energy to at least a portion of ventricular tissue ofthe heart, wherein the vibrational energy stimulates contraction of atleast one ventricle.
 2. A method as in claim 1, wherein the vibrationalenergy is selectively directed at left ventricular tissue.
 3. A methodas in claim 1, wherein the vibrational energy is selectively directed atright ventricular tissue.
 4. A method as in claim 1, wherein thevibrational energy is directed at both left and right ventriculartissues.
 5. A method as in any one of claims 1 to 4, wherein thevibrational pacing energy is directed as one or more narrow beams.
 6. Amethod as in any one of claims 1 to 4, wherein the vibrational pacingenergy is directed as one or more wide beams.
 7. A method in any one ofclaims 1 to 4, wherein the vibrational pacing energy is directed as anycombination of one or more narrow or wide beams.
 8. A method as in anyone of claims 1 to 4, wherein the vibrational pacing energy is deliveredfrom a single implanted enclosure.
 9. A method as in any one of claims 1to 4, wherein the vibrational pacing energy is delivered from two ormore implanted enclosures.
 10. A method as in any one of claims 1 to 4,wherein the vibrational pacing energy is delivered from an externalvibrational transducer.
 11. A method as in any one of claims 1 to 4,further comprising programming delivery of the vibrational energy topromote synchronized contraction of the left and right ventricles.
 12. Amethod as in any one of claims 1 to 4, further comprising electricallystimulating one or more regions of the heart in a coordinated patternwith the delivery of the vibrational pacing energy.
 13. A method as inany one of claims 1 to 4, further comprising detecting the presence orabsence of cardiac signals originating in the ventricles or atria of theheart and triggering or inhibiting the delivery of electrical orvibrational energy based on programmed parameters.
 14. A pacing systemcomprising: an implantable enclosure having circuitry for controlling avibrational transducer under conditions selected to stimulate heartcontraction when directed at cardiac tissue.
 15. A pacing system as inclaim 14, wherein the circuitry comprises a power amplifier, animpedance matching circuit, and a signal generator for controlling thevibrational transducer.
 16. A pacing system as in claim 15, furthercomprising circuitry for generating electrical pulse(s) for stimulatingheart contraction and circuitry for detection of intrinsic cardiacsignals.
 17. A pacing system as in claim 16, further comprisingcircuitry which analyzes detected intrinsic heart signals and whichcontrols the electrical pulses and vibrational pacing to synchronizecontraction of the left and right ventricles.
 18. A pacing system as inclaim 17, wherein the electrical pulse circuitry and detection circuitryis located in the same enclosure as the vibrational transducercircuitry.
 19. A pacing system as in claim 14, wherein the vibrationaltransducer is located within the enclosure.
 20. A pacing system as inclaim 14, wherein the vibrational transducer is connected to theenclosure by a cable.
 21. A pacing system as in claim 14, wherein one ormore vibrational transducers are located on a lead and positioned in theright ventricle.
 22. A pacing system as in claim 14, wherein one or moretransducers are located on a lead and positioned in a subcutaneouslocation.
 23. A pacing system as in claim 14, wherein one or moretransducers are located on a lead and positioned in the right atrium.24. A pacing system as in claim 14, wherein a vibrational transducer isdirected to ventricular tissue.
 25. A pacing systems as in claim 14,wherein a vibrational transducer is directed to atrial tissue.
 26. Apacing system as in claim 14, wherein a vibrational transducer isdirected to both atrial and ventricular tissue.
 27. A system as in claim14, wherein the enclosure is adapted to include a cardioverterdefibrillator.
 28. A system as in claim 27, wherein the cardioverterdefibrillator uses electrical energy.
 29. A system as in claim 27,wherein the cardioverter defibrillator uses vibrational energy.
 30. Apacing system comprising: a vibrational transducer; and controlcircuitry for activating the vibrational transducer in order to delivercontrolled vibrational energy to a target region of the heart underconditions selected to promote synchronized contraction of theventricles.
 31. A pacing system as in claim 30, wherein the vibrationaltransducer is adapted to contact an exterior surface of the patient'sskin and deliver the vibrational energy through the tissue overlying thetarget region of the heart.
 32. A pacing system as in claim 31, whereinthe control circuitry comprises a power amplifier, an impedance matchingcircuit, and a signal generator for activating the vibrationaltransducer.
 33. A pacing system as in claim 32, further comprisingcontrol circuitry which analyzes detected intrinsic heart signals andwhich controls the vibrational energy to promote synchronizedcontraction of the ventricles.